function [ status, code ] = mx_eyelink_is_connected( )
%MX_eyelink_is_connected Checks whether the connection to the tracker is alive.
% 
% Remarks:
% Call this routine during loops and wherever the experiment might lock up if 
% the tracker is shut down. Exit the experiment (by terminating loops and 
% returning from all calls) if this returns 0.
% Returns:
% 0 if link closed.
% -1 if simulating connection.
% 1 for normal connection.
% 2 for broadcast connection (NEW for v2.1 and later).
%
%----------------------------------------------------------------------------
% Copyright Eduardo Aponte 2013
% aponteeduardo@gmail.com